LED Tester

Or $1.34 plus 50 cents shipping if you do eBay:  # 291646391480

I missed that one. Mine was $2.94 including shipping. (battery not included)

Not bad for 2 or 3 bucks.  Do we know if it is accurate on the ma ratings?  

I'll have to sacrifice a couple leds. I used 20ma and 100 ma to try it out without problems.

JohnGaltLine posted:

Not bad for 2 or 3 bucks.  Do we know if it is accurate on the ma ratings?  

Use your meter and test it with a suitable LED in series.

stan2004 posted:

Or $1.34 plus 50 cents shipping if you do eBay:  # 291646391480

Thanks, Stan; just ordered one.

Certainly cheap enough, with all the LED's I use, I should have one.

Nice find!  Thanks for the post.

Dave

They have been out for a number of years. Because I got the one I have at least 2 years ago. Its the same one you speak about.. And cost about the same price you guys paid for yours.

Now that we have a couple more knowledgeable Johns than me on board, what do the symbols on the bottom row mean?

Well, they have a diagram of a bi-color 3-lead LED, so I presume somehow they're testing those.  The ACA is a common cathode LED and the CAC is a common anode LED.  I'm not entirely sure exactly how the test works as I don't see a spot for the 3rd LED lead.  I think instructions would be useful, maybe there's a clue there.

Since Scot has had one for several years, maybe he can tell us.

No instructions in that trip from Hong Kong with my package.

John H posted:

Now that we have a couple more knowledgeable Johns than me on board, what do the symbols on the bottom row mean?

My only thoughts are that it could just be a 'reference' section to remind you which one is the anode and which is the cathode.   I know I would make plenty of use out of that, been a life long struggle since I learned what a diode was when I was like 6 years old.  

I think JLG may be on to the meaning.  They're just reminding you which configuration is which.  You obviously still have to test the two colors one at a time.

As for the currents, I'm guessing it's actually pretty simple.  There is probably a string of surface mount resistors inside that they use to set the current.  Obviously, they won't be dead on for different voltage rated LED's, some light at less then 2V, red, green, etc.  Others light at more than 3V, white, blue, etc.  I suspect it's just an approximation of the current based on a median voltage rating.  The red/green probably get a bit more current, the white/blue probably a little less.  For the price, I can't imagine any other construction.  Maybe Scot will take his apart...

gunrunnerjohn posted:

JohnGaltLine posted:

Not bad for 2 or 3 bucks.  Do we know if it is accurate on the ma ratings?  

Use your meter and test it with a suitable LED in series.

If room permitted, I would add two small test jacks in series with battery lead, so I could plug in a current meter if I really HAD to know that exact current draw.  When not needed, place a shorting bar across the jacks.

Granted gilding the lily as they say on a 2-3 dollar item.

I think I'd just check it once to see if it's close and not bother with the extra work of a jack.   If my guess is correct at to the internal configuration, it's not going to change as long as the battery is good.

I think GRJ is probably correct with the resistor bank theory.  

All I meant by asking if the ratings were accurate was, are they reasonably accurate.  I've had some cheap devices with ratings or meters that are so far off that there is no point in it being there, such as a battery charger that would display a 100 mA load when it was delivering 1 amp and melting my batteries.  

JGL

I agree that I'd probably check it once, just to have confidence that it wouldn't cook my LEDs.

I don't have any in  cars or engines but use some in layout lighting so I just use low voltage from a transformer. Have used a cell phone  charger too.

Great device for checking intensity also for resistor selection.

The Top row has the + and - markings for single diode on left of device

I believe on the bottom (2) row your 2 leads go in one row and the common goes in the other row.  So you can test Bi-directional also.  The markings on the right tell you which row to put the common lead in.   G  (another night in a holiday in )

George, I thought of that, but the higher MA grads on the connector makes me wonder exactly how this is wired.  Also, if they intended a 3-lead LED to go into the and bottom, I'd have thought they'd put the rows a bit closer together.  They way they are, you'd be bending the leads pretty far to get the middle lead to the bottom row.

Before I sacrifice any LED's to it, I think I'd check the internal wiring to see what they're doing.

Another thought is that the same case may be used, or may have once been used, for a similar product with a third row of pins, so you could plug in bi-color LEDs?  Just guessing at this point.

I may have to get one just out of curiosity!

Here's the last photo in the eBay listing.  Too bad the bottom row is hidden by the battery.  It is not obvious how one would know from the case-side markings which sockets to use for 3-pin LEDs.  I'm surprised no one has pondered why their own photo shows 2-lead LEDs plugged into the bottom slots!  

If you plug in all three leads wouldn't you get both colors at once?

Just as important Stan is why that seemingly standard 20ma LED isn't going up in smoke plugged into the high current output!   All the LED's plugged in at once would seem to overtax the capability of one little 9V battery, maybe that's it...

As John H says, if you plugged in all three leads and powered them, both colors would light.  Truthfully, for testing the three lead LED's, the upper row is fine, you plug the common into the - or +, depending on the polarity of the bi-color LED and just connect the other leads one at a time to test each side.

I think I've "scoped" out the meanings of the A-C-A or C-A-C where they are.  You just use that 20ma section to test those as I described, or as I said, test them on the upper row at various currents.  I think we're probably trying to make this too complicated.

Ordered mine a few days ago. Beats scronging around for test clips and resistors

I just ordered one on Amazon. 

OK,about the tester Thanks, John

You'll probably be waiting for that tester from Amazon as long as the eBay ones, they're shipping from the Far East

They should work on their descriptions as well.  18 watts?  Powered with a CR2032 battery?  I think not!

gunrunnerjohn posted:

You'll probably be waiting for that tester from Amazon as long as the eBay ones, they're shipping from the Far East

Estimated Delivery Date: Feb. 4 - 23 when you choose Standard at checkout.

Ships from and sold by FAR CLOUD.

 

They should work on their descriptions as well.  18 watts?  Powered with a CR2032 battery?  I think not!

 

Part Number	3
Shape	arc
Wattage	18 watts
Type of Bulb	LED
Special Features	Powered by a 3V CR2032 battery.

And if memory serves, Aren't white LEDs 4V or so to light?  3V battery plus though a current resistor would drop voltage to where the white would not light or lights in some off white color.  But just a guess.

Most white LED's will light at around 3.2-3.3 volts, but that leaves no headroom for current limiting.  I'm sure the pictures of the same unit with the 9V battery are a lot more accurate.

Yep ,Thanks,John

stan2004 posted:

Here's the last photo in the eBay listing.  Too bad the bottom row is hidden by the battery.  It is not obvious how one would know from the case-side markings which sockets to use for 3-pin LEDs.  I'm surprised no one has pondered why their own photo shows 2-lead LEDs plugged into the bottom slots!  

Yes it is, as I mentioned they show common Anode and common cathode on the left.  The right concurs with the + and - markings.

Also, you do see one of the bottom rows.  Notice how the middle doesn't have a resistor, but two outer do.  This is in a three pin segment.

I ordered one too, and will check it out, but this looks like it will work fine.  Additionally with a molex connector with pins you should be able to test 1.5V, 6V and 18V bulbs with this too.   G

You get what you pay for:-)  I got mine yesterday.  Here is what I found:

9V battery barely fits in the case, you have to press it in, be careful of wires.

Top row is + as marked, and entire second row is negative.

The Top row doesn't really have a series of resistors, only 4 values.

From left first 3 are 1500 ohms, next 3 are 681 ohms, next 4 are 360 ohms, and last 2 are 240 ohms.

Bottom 2 rows is where it gets interesting.

Across top you have +360  negative  +360  open  +120 open +120  +120 open +120 +51 open +51

Across bottom have neg 360 Positive the rest are all negatives.

My 51 ohm resistor was bad (open).  G

Stan,

I have two lead LEDs that are 100ma, so they need to go in the bottom slot to test them.

Well, it was only around $2.

True.  It is a good basis for testing though, I am going to wire in a few 2 pin molex connectors so I can test 1.5, 6V bulbs and LEDs and probably will change a few resistors to get a better test of LED brightness.  G

Got the LED tester, interesting they didn't actually use the properly sized resistors to actually provide the currents they specified.  Mine came without the screws, so I had to find a couple.  Indeed, the battery is a VERY tight fit!  I measured the currents, the 2ma was way high at 4.5ma with a white LED.  They have a 1500 ohm resistor to drop the 6V, it should be around 3K to give you 2ma with white LED's.  I might put a 3K in the first slot so I have a low current test, then just leave the others.  As noted, it only has four resistor values, so obviously it only does four currents in reality.  I didn't test the bottom row, but I do have some 100ma LED's, I might try one of those.